Weathering tests designed to evaluate weatherability of organic materials such as coatings include an outdoor exposure test in which a test piece is exposed to the weather and a traced and collected sunlight exposure test in which a test piece is exposed to traced and collected sunlight. In addition, special test methods include an artificial accelerated weathering test in which a test piece is irradiated with light from an artificial light source by means of a weathering apparatus, such as a sunshine weather meter, a UV carbon weatherometer, a xenon weatherometer, a dew panel weatherometer, and a metal halide weatherometer.
JP-A-48-60695 discloses a method for accelerating a salt spray test for evaluating anticorrosion of steel stock against seawater, in which hydrogen peroxide-added salt water is used as testing seawater.
The above-mentioned outdoor exposure test and traced and collected sunlight exposure test require an extremely long period of time not shorter than several months for test pieces to be deteriorated. It has been impossible with these weathering tests to evaluate weatherability rapidly.
The problem of the artificial accelerated weathering test, on the other hand, is that the test fails to sufficiently reproduce the deterioration that should have been resulted from exposure to natural weathering conditions. That is, the deteriorated state of a test piece does not agree with that in the outdoors for the following reason. When articles or materials are long-term exposed outdoors, their deteriorated surface, typically the coating film, shows a surface profile with fine waviness and fine pits in a mixed state, both of which reduce the surface gloss, whereas the surface profile developed in the accelerated weathering test mainly displays fine waviness so that the reduction in gloss as observed is chiefly ascribed to the fine waviness alone.
The above-described improved salt spray test aims at acceleration of a durability test, but its application is limited to evaluation of anticorrosion of steel stock against seawater in special fields. It does not apply to weatherability testing of organic materials or articles thereof.